Variable pressure hydraulic system



June 1, 1965 s. 'r. HOGG 3,186,173

VARIABLE PRES SURE I HYDRAULI C SYS TEM Filed Sept. 15. 1960 INVENTOR.Stanley T. Hogg ATTORNEY United States Patent C 3,186,173 VARIABLEPRESSURE HYDRAULIC SYSTEM Stanley Thomas Hogg, Merrick, N.Y., assignorto American Machine & Foundry Company, a corporation of New Jersey FiledSept. 15, 1960, Ser. No. 56,165

1 Claim. (Cl. '60---54.5)

This invention relates in general to hydraulic systems and, moreparticularly, to hydraulic systems wherein the pressure may bevariedover a wide range.

An object of this invention is to provide a hydraulic system which iscapable of more versatile operation from a constant in'put pressuresource. 7

Another object of this invention is to provide a hydraulic system havingaworking cylinder and a pressure intensification cylinder in which aninfinite variety of pressures up to the maximum pressure produced by thepressure intensification cylinder may be applied to the workingcylinder.

A further object of this invention is to provide a simple pressureintensification system which may be used in connection with a hydraulicwork producing device to increase the force which may be applied by thework producing device.

A still further object of this invention is to provide a hydraulicsystem in which a given pressure source and a given work cylinder may beused to apply a greater working force.

Still another object of this invention is to provide a hydraulic systemwhich is simple in its construction and which requires fewer hydraulicconnections to apply a wider range of pressures to a hydraulicallyoperated device.

Yet another object of this invention is toprovide a hydraulic system toactivate a work cylinder and move its piston rapidly against little orno resisting force and in which the work cylinder may be furtheractivated by the hydraulic system to move more slowly and apply a largerforce.

Additional objects, advantages and features of invention reside in theconstruction, arrangement and combination The hydraulic fluidthen flowsthrough the smaller end 19 of the pressure intensification cylinder 60and then through pipe 17 into a work cylinder generally designated onthe piston rod 13 to urge jaw 12 towards the fixed jaw 11. Therefore, asshown in the drawing, when pressure of parts involved in the embodimentof the invention and its practice as will be understood from thefollowing description and accompanying drawing wherein:

The single figure of the drawing is a schematic illustra tion of theinvention with the work cylinder and the pressure intensificationcylinder shown in longitudinal crosssection.

Referring to the drawing in detail, a pipe, tube, hose or the like isdesignated by the reference numeral 33 and is connected to a source ofhydraulic fluid under pressure. The source of hydraulic pressure mayb'ea pump 41 which draws hydraulic fluid 37 from the sump 36 through thetube 42, or the source of hydraulic pressure maybe a manifold whichsupplies hydraulic fluid under pressure to other devices on an existingmachine. On one particular machine a manifold pressure of 250 pounds isapplied to pipe 33 as this pressure operates other mechanisms andtherefore cannot be varied. When the two-way valve 34 is turned so thathydraulic fluid under pressure may flow from pipe 33 into pipe 32, thepressure regulating valve or controlled pressure drop valve 30 allowshydraulic fluid to pass through it until the pressure for which thevalve 30 is set builds up in pipe 27 to the pressure for which thepre-set valve 34 is set. A pipe 29 bypasses the controlled pressure dropvalve 30, but the higher pressure in pipe 32 cannot flow about thecontrolled pressure drop valve 30 through the bypass 29 because thecheck valve 28 blocks it. The hydraulic fluid at the selected lowerpressure which passes through the controlled pressure drop valve 30flows through pipe 27 and through the port 40 in the smaller end 19 ofthe pressure intensification cylinder which is generally designated bythe numeral 60.

from a hydraulic pressure source flows through pipe 33 and past valve 30with a controlled pressure into the work cylinder 50, the hydraulicfluid at a selected pressure will urge the piston '15 to the right sothat the work pieces 26 will be held between the jaws 11 and 12. If thesource of hydraulic pressure which is connected to pipe 33, such as pump41, can only deliver a given number of cubic inches of hydraulic fluidper second at a given-pressure, a relatively small diameter workcylinder 5%) will more rapidly move jaw 12 towards jaw 11 to grip thework pieces 20.

When the work pieces 20 are clamped between the jaws 11 and 12 as shownin the drawing, the force exerted on the work pieces 29 by the jaws 11and 12 will be determined bythe area of the piston'face of piston 15 andthe pressure which the pressure regulating valve 30 is set to pass. Byvarying the setting of valve 30 from zero to the pressure available fromthe hydraulic pressure source, a range of forces may be applied to jaw12 by the work cylinder 50.

When it is desired to apply greater force on work pieces 20 by jaw 12,the line valve 26 is opened allowing hydraulic fluid to flow behindpiston 22 within the large portion 18 of the pressure intensificationcylinder 61]. The larger area of the piston face of piston 22 comparedto the piston face of the pressure intensification piston 23 causes thepistons 22 and 23 to move to the left as shown in the drawing. As piston23 moves to the left, it passes the port 40 and effectively closes it sothat hydraulic fluid cannot flow from the smaller portion 19 of thepressure intensification cylinders!) back down pipe 27. As additionalhydraulic fluid at a controlled pressure flows past valve 30 and valve26 through pipe 25 into the pressure intensification cylinder 60, thepressure in the smaller portion 19 of the pressure intensificationcylinder becomes a multiple of the pressure passed by pressureregulating valve 30 and exerted on the larger piston 22. The multiple bywhich the pressure intensification'cylinder increases the pressure isdetermined by the ratio of the areas of the piston faces of piston 22and the pressure intensification piston 23. As the pressureintensification piston 23 moves further to the left as shown in thedrawing, hydraulic fluid under this intensified pressure flows throughpipe 17 to exert a correspondingly increased pressure on piston 15. Theincreased pressure on piston 15 increases the force exerted on themovable jaw 12 which then more tightly clamps the work pieces 20.

After a desired operation is performed on the work pieces 20 while theyare clamped between the jaws 11 and 12, the two-way valve 34 is turnedso that pipe 32 is connected to drain pipe 35 which leads to the sump 36which catches hydrauluic fluid 37 draining from the system. When pipe 32is connected to drain '35, pressure in pipe 32 falls to Zero. Within thework cylinder 50 a compression spring 16 is constantly urging piston 15to the left. In a like manner, a spring 24 in the pressureintensification cylinder 69 is constantly urging the pistons 22 and 23to the right. The spring 24 urges piston 22 to the right forcing fluidwithin the large portion 18 of pres sure intensification cylinder 60 toflow out through pipe 25 When it is again desired to activate workcylinder 50 i and close jaws 11 and 12, valve 34 is again set to connectpipes 33 and 32 whereupon the cycle may be repeated. It is to be notedthat if the valve 26 is left closed, the regulating valve 30 may be usedto directly control the hydraulic pressure Within the work cylinder 50and the force exerted by jaw 12 on the work pieces 20.

If an existing machine has a work cylinder or other hydraulic deviceactivated from a source of hydraulic fluid under pressure through acontrolled pressure drop valve to vary the force exerted by the workcylinder, a relatively simple modification of an existing machineaccording to this invention may increase the force exerted by the workcylinder by any desired multiple. For example, in certain cut-offmachines on the market having a work-holding fixture actuated byhydraulic pressure, supplied from a hydraulic source through a manifold,the pressure in the hydraulic manifold is of a constant value whichcannot conveniently be changed for the reason that such machines havevarious other elements activated from the manifold. This invention isreadily adapted to such machines where it is desired to have a Widerrange of clamping force on the work-holding fixture.

Thus the invention may be readily adapted to existing machines as wellas being easily built into new machines. If this invention is applied toan existing machine, the machines hydraulic system need not be affectedas the machine may be conventionally operated without activating thepressure intensification cylinder.

The arrangement of the valve 30 with the pressure intensificationcylinder 60 permits an infinite selection of pressure values to the workpistion 15 from zero to a value equal to the product of the value of thepressure source by the pressure intensification cylinder multiple.Pressures less than the pressure source may be obtained by closing thevalve 26 so that the pressure intensification cylinder is bypassed.Pressures above the source pressure may be obtained by opening the valve26 and suitably adjusting the valve 30.

The spring 24 should be set to counter-balance piston 22 to resist ahydraulic force greater than the hydraulic force on piston 15 resistedby spring 16. This assures that the port 40 will not be closed until thejaw 12 has contacted the workpiece.

Although a work piece holding device is shown being activated by thework cylinder 50, this invention may be used for many other purposes.

While I have disclosed my invention in the best form known to me, it isto be understood that this is purely 4 exemplary and that modificationsin the construction, arrangement and combination of parts and thesubstitution of equivalents mechanically and otherwise may be madewithout departing from the spirit of the invention except as it may belimited in the appended claim.

I claim:

In a hydraulic system, a reservoir for hydraulic fluid, said reservoirconnected through a source of hydraulic fluid under pressure, acontrolled pressure drop mechanism in a line from the source ofhydraulic fluid under pressure, a two way valve which in a firstposition connects the controlled pressure drop mechanism to the sourceof hydraulic fluid under pressure and in a second position communicatesthe controlled pressure drop mechanism with the reservoir, a check valveconnected across the controlled pressure drop mechanism to permit flowonly from the outlet of the controlled pressure drop mechanism to theinlet thereof, said two way valve thus being operable to selectivelydirect fluid from said source of hydraulic fluid under pressure towardsaid controlled pressure drop valve and from said check valve to saidreservoir, a pressure intensification cylinder having a larger portionand a smaller portion, a piston having a larger portion and a smallerportion reciprocable in said larger portion and said smaller portion ofsaid cylinder, respectively, the smaller portion of the cylinder havinga side port, a spring in the pressure intensification cylinder biasingthe piston to its retracted position, a first conduit communicating thepressure drop mechanism to the side port, said port being incommunication with the working chamber of the intensification cylinderwhen the piston is in the retracted position, and a second conduitcommunication the pressure drop mechanism to the larger portion of thepressure intensification cylinder, a valve in said second conduit, ahydraulic motor having a piston therein, said motor communicating withthe smaller portion of said pressure intensification cylinder, and meansnormally biasing the piston in said hydraulic motor to its inactiveposition.

References Cited by the Examiner UNITED STATES PATENTS 1,888,990 11/32Kurath -545 2,032,185 2/36 Sciaky 60-545 2,102,865 12/37 Vickers 60-522,286,620 6/42 Hollengreen 6097 X 2,403,912 7/46 D011 60-545 2,580,35312/51 Hunt 60-545 2,656,745 10/53 Forichon 60 54.5

FOREIGN PATENTS 704,657 4/41 Germany.

JULIUS E. WEST, Primary Examiner.

SAMUEL LEVINE, ROBERT R. BUNEVICH,

Ex mi

